This invention relates to an intake assembly for a multi-cylinder internal-combustion engine comprising at least two intake ducts of different lengths for each cylinder which start out from an intake distributor and converge shortly before the intake valve, and in which a shut-off device is provided for the shorter intake duct.
An intake manifold assembly is known from Published German Patent Application No. DE 4,040,598. This assembly has first and second intake ducts of different lengths for each cylinder, which intake ducts each start out from a first or from a second intake distributor.
An intake duct comprising a throttle valve leads into the first intake distributor which is connected with the second intake distributor by means of a pipe.
In the second intake distributor, a rotary shield is arranged which has a wall curved in the shape of a graduated circle which interacts with a correspondingly curved wall of the intake distributor. By switching of the rotary shield, the second intake distributor can be activated or shut off.
In such a device, it is important to achieve a good seal between the individual intake ducts. This means that a very high accuracy of fit is required during the manufacturing of the individual elements. If the intake assembly is formed of plastic, the high accuracy of fit can be achieved only by means of relatively high manufacturing expenditures.
An intake manifold assembly of this type is also described in U.S. Pat. No. 4,643,138 (=EP 177,794). In this case, the individual intake ducts are combined with a collecting intake duct to form a unit to which the intake distributor is flanged as a separate component. This intake distributor is connected on one side with the collecting intake duct through a throttle valve and, on the other side, it is connected with the individual intake ducts. The two individual intake ducts may be shut-off or opened up by means of flaps which are arranged on shafts. The manufacturing of this known intake manifold assembly results in relatively high expenditures and presents problems with respect to a perfect interaction of the pivotable flaps disposed in the intake distributor with the second individual intake ducts arranged in another component.